1. Field of Invention
This invention relates to internal combustion engines and to both spark-ignited and diesel operated engines, and particularly to improvements in the engine combustion chambers.
2. Prior Art
The diesel engine is a highly efficient converter of fuel energy into mechanical energy. Brake thermal efficiencies in excess of 50% have been proven in production two-cycle diesels that are highly turbocharged. Diesel engines gain this significant efficiency mainly by avoiding throttle losses and by having a generous expansion ratio. The engine load is controlled solely by reducing or increasing fuel consumption. Fuel is burnt rapidly, and completely, even when the engine is lightly loaded. At all times the heat so produced is expanded by means of a large and efficient expansion ratio. Because of these factors, diesel engines exhibit significant potential to meet current and future demands for reduced emissions and high fuel economy. However, the advantages are to a large extent sacrificed when a diesel engine is designed to fill the exacting requirements of vehicular use, and must conform to performance standards set by spark-ignited gasoline engines. The main disadvantage of diesel engines lies in the requirements of high working pressures to make the cycle of operations practical. The engines are subjected to high peak cylinder pressures requiring a high degree of attention to material strength and tolerances used in their manufacture. Generally, for a given output, diesel engines cost twice as much to manufacture as a gasoline engine of comparable output. Even with the best alloys, diesel engines are invariably heavier than gasoline engines. Further, the demands of the combustion process on the injection system make very high speeds difficult to achieve efficiently. The high peak pressures occurring during combustion also create shock waves that are transmitted through the engine castings, producing objectionable noise and torsional vibrations that are difficult to control. Power flow is not as smooth as an equivalent gasoline engine.
In order to approach the normal operating speeds of current gasoline engines, a diesel engine combustion system requires a high degree of turbulence and mixing in the combustion chamber in order to rapidly and completely mix the fuel and air in the relatively short time available for combustion. While this works well, and comparatively high engine speeds can be obtained, the high degree of mixing and turbulence degrades the diesels' efficiency. Agitation of air takes place during the compression process, and this compression must result in the attainment of a sufficiently high temperature to readily ignite the injected fuel. Energy losses caused by high turbulence and swirl materially reduces the desirable heat of compression. To compensate for this loss, high speed diesels require a higher compression ratio. This further increases the peak cylinder pressures and increases the heat transfer losses out of the combustion chamber due to the high turbulence and its scrubbing effect on the thermal layer of air that insulates the combustion gases.
Thus, completion of the diesels' complex combustion process in the short time available as the piston approaches top dead center, is the major reason for deficiencies in performance when compared to gasoline engines. The present invention anticipates introduction of a diesel engine with all of the inherent advantages, while being significantly smaller, cleaner, quieter and more powerful without a loss in durability, and without an increase in weight or decrease in efficiency.
There have been many previous attempts to decrease the time required for the combustion process to be completed. These past efforts have all centered on ways to complete combustion near top dead center and in the current cycle of rotation of the engine.
A review of earlier concepts involving multiple chambers communicating with individual cylinders of an internal combustion engine reveals two patents issued to one R.D Lampard, namely U.S. Pat. Nos. 4,248,192 and 4,641,616. Each of these publications disclose a main combustion chamber and a pilot charge chamber. Combustion is initiated in the pilot charge chamber, and then the pilot charge and the main charge are brought together by means of selective timing of a valve mechanism. Although the valve mechanism would initially appear to be of the general configuration of the valve in the present concept, the function is completely different. In both of these patents, combustion always occurs while the piston is passing over top-dead-center (TDC). The combustion process is never removed from the cycle during a complete revolution of the engine, but rather is "delayed" for a short period of time. The patents also focus on configuration providing a different compression ratio in each combustion chamber, high compression created in the main chamber and low compression in the pilot charge chamber. The preferred embodiment disclosed is directed to spark-ignited gasoline engines.
U.S. Pat. No. 2,197,901 issued to Smith presents a four-cycle, spark-ignited engine which relies on two chambers for each combustion to occur during each cycle, again, not being separated by means of a full rotation of the crank shaft. U.S. Pat. No. 892,296 issued to Oberhansli, the DeMalvin DeMontazet, et al., U.S. Pat. No. 1,892,040 and U.S. Pat. No. 1,653,825 granted to Saives each seek to complete combustion near top-dead-center during the combustion producing portion of the cycle in some combination of main and prechambers. Communication between chambers is determined by the timing of a valve.
The Trucco U.S. Pat. No. 4,372,264 provides a means utilizing a small fraction of the combustion products from the prior combustion process in either a spark-ignited or a diesel engine, to "preheat and vaporize" a small amount of relatively poor quality fuel in a prechamber. The prechamber is isolated from the main chamber by valve means. Here, again, combustion occurs over a relatively short period of time when the piston is near top-dead-center, and not over a potential of 360.degree. of crank shaft rotation, as disclosed herein.
The U.S. Pat. No. 1,204,986 granted to Irwin teaches protection of a spark plug from the fuel/air mixture, until just prior to the beginning of combustion, in order to minimize spark plug fouling. Combustion occurs rapidly near top-dead-center of the crankshaft rotation.